1. Field of the Invention
The invention relates to the field of cable television systems and, in particular, to transmitting advertising information from a cable headend to a subscriber unit of a cable television system and applying the transmitted advertising information to a television receiver display attached to the subscriber unit.
2. Prior Art
In the prior art it is well known for large numbers of homes subscribing to cable television systems to receive a number of commercial and public television signals by way of transmission cables. Each television signal includes video and audio signals, which can be transmitted along a coaxial cable by a system headend within a discrete frequency band known as a channel. The subscriber tunes a television receiver to the desired channel and receives a composite television signal.
It is known to transmit information in addition to the television signals to the subscribers of prior art cable systems during blank field intervals of the video signals. For example, U.S. Pat. No. 4,288,809, issued to Yabe, describes transmitting alphanumeric information during the blank field intervals. The alphanumeric information is stored in a temporary memory for display on a television receiver within a subscriber unit. Yabe further describes an index that permits the viewer to determine by an overlay on the screen what information is available. The index is contained on a RAM which can be updated by the blank field interval transmitted data.
U.S. Pat. No. 4,161,728, issued to Insam, also discloses means for displaying information sent during field blanking of video information. The Insam patent describes a memory unit for storing information to be displayed, a display unit for synchronizing and producing addresses to memory containing the information to be displayed, a decoder unit, a control unit which is accessible through remote control, and a microprocessor which is responsive to programmed instruction.
U.S. Pat. No. 4,052,719, issued to Hutt, also describes the transmission of auxiliary information during the field blanking intervals of video signal transmission. On the receiving end, a television system has a RAM for collecting and storing the transmitted information, a selector, and a reading device. The viewer has the choice of viewing the video signal or the auxiliary information separately or together on the screen.
It is also known for stored advertising information to be displayed on television receivers such as the television receiver found in cable television systems. For example, U.S. Pat. No. 4,344,090, issued to Belisomi, discloses a picture display device using a ROM to store coded data corresponding to a television image in memory. The coded data represents advertising information that can be viewed upon demand and can be superimposed upon a received video signal or viewed as an alternative to the received video signal. Pococh, U.S. Pat. No. 4,941,041, also teaches a system for selectively delivering television video for advertising.
U.S. Pat. No. 5,233,423, issued to Jernigan, teaches a television receiver equipped with a graphics generator capable of generating single or multiple graphic images from data representing advertisements permanently stored in a local memory device. Images corresponding to the advertisements are displayed when a control function of the receiver is activated.
However the advertising information of the above described systems cannot be updated because it is permanently stored in the local devices.
It is therefore an object of the present invention to provide a display of a visual image on a television receiver in a subscriber unit of a cable television system.
It is a further object to provide such a display of a visual image that can be updated.
It is a further object of the invention to transmit the updated images to the subscriber unit of the cable television systems over the same transmission cable as the cable television signals.
These and other objects and advantages of the invention will become more fully apparent from the description and claims that follow or may be learned by the practice of the invention.